Application of rubber O-rings in reciprocating mechanical motion

Rubber O-rings are extrusion seals. The basic working sealing principle of extrusion seals is to flexibly deform through the sealing ring, but cause contact pressure on the sealing contact surface. The contact pressure is greater than the internal pressure of the sealing medium and will not leak. Otherwise it will leakage. DLSEALS tell you that in order to ensure effective sealing effect, the characteristics of the sealing material and the design of the sealing structure are crucial links. For different types of sealing structures, the compression amount and groove design of the O-ring seal are different. The sealing forms of safety valve O-rings mainly include end static sealing rings, reciprocating sealing rings and valve seat sealing rings, with different characteristics and structural designs.

So, what are the requirements for the reciprocating sealing structure design of rubber O-ring seals? Taking the pilot safety valve seal as an example, the structural design requirements of the reciprocating seal are briefly explained.

The seal between the main valve disc and the guide pillar of the pilot safety valve is a reciprocating sealing ring. Since the suffocation valve is a normally closed gate valve, the movement frequency is generally very low and the movement period is very short. Under normal operating conditions, there is a radial static seal between the valve disc and the guide pillar, and repeated movement can only occur during the opening and closing process of the safety valve. When the safety valve opens, the main valve disc moves upward. When the safety valve is closed, the disc side of the main valve moves downward. Unlike general mechanical reciprocating seals, O-rings like to be squeezed in the axial direction.

In order to ensure the initial sealing effect without affecting the movement characteristics of the gate valve, the groove design of the O-ring seal should consider controlling axial deformation. The axial compression rate should be controlled within 10%-15%, and the pipe groove roughness should be kept below Ra0.8pm. When high pressure moves repeatedly, the O-ring is easily extruded and a retaining ring must be installed.

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